public class Test2 {
    public static void main(String[] args) throws InterruptedException{
        Thread[] threads=new Thread[20];
        for (int i = 0; i < 20; i++) {
            int n=i;
            threads[i]=new Thread(()->{
                System.out.println(n);
            });
        }
        for (Thread t:threads) {
            t.start();
        }
        for (Thread t:threads) {
            t.join();
        }
        System.out.println("OK");
    }
}
